Many operations in a subterranean borehole involve the setting of tools that are mounted outside of a tubular string. A common example is a packer or slips that can be used to seal an annular space or/and support a tubular string from another. Mechanical actuation techniques for such devices, which used applied or hydrostatic pressure to actuate a piston to drive slips up cones and compress sealing elements into a sealing position, involved openings in the tubular wall. These openings are considered potential leak paths that reduce reliability and are not desirable.
Alternative techniques were developed that accomplished the task of tool actuation without wall openings. These devices used annular fluid that was selectively admitted into the actuator tool housing and as a result of such fluid entry a reaction ensued that created pressure in the actuator housing to operate the tool. In one version the admission of water into a portion of the actuator allowed a material to be reacted to create hydrogen gas which was then used to drive a piston to set a tool such as a packer. Some examples of such tools that operate with the gas generation principle are U.S. Pat. No. 7,591,319 and US Publications 2007/0089911 and 2009/0038802.
These devices that had to generate pressure downhole were complicated and expensive. In some instances the available space was restricted for such devices limiting their feasibility. What is needed and provided by the present invention is an actuator that goes in the hole with stored potential energy that employs a variety of signaling techniques from the surface to actuate the tool and release the setting pressure/force. The preferred potential energy source is compressed gas. Those skilled in the art will further understand the invention from a review of the description of the preferred embodiment and the associated drawings while further appreciating that the full scope of the invention is to be determined by the appended claims.